(1) Field of the Invention
The invention relates to a margin inspector for IC wafers, and more particularly to an inspecting apparatus helpfull to visibly examine the washout margin of an IC wafer after a coating process.
(2) Description of the Prior Art
Conventionally, in the process of coating a PR layer or the like membrane onto a wafer, the manufacturing device usually washes out a periphery ring of PR or the like material by a substantial width along the circular edge of the wafer for forming a concise available area thereinside on the wafer. Generally, the allowable width of such periphery ring is ranged between 1.0 mm and 2.0 mm. As long as the width of the periphery ring falls into the allowable range, the wafer is deemed as qualified to proceed the next manufacturing process. Yet, once the width of the periphery ring on a wafer falls beyond the allowable range, the wafer is deemed as an ill-conditional one and needs further amendment.
One of the tools in the art to examine the specifications of the washout periphery ring on a wafer is the microscope. However, the investigation on the periphery ring by a microscope usually implies time-consuming work. To save time and labor in examining the ring, survey by eyesight is usually applied in the field. Yet, one of the disadvantages in eyesight survey is the problem in accurately locating an ill-conditional wafer. Disputation on the qualification usually arises while a wafer is on the verge of allowance; i.e. the width of the periphery ring is around 2.0 mm or 1.0 mm. In the case that a qualified wafer is accidentally determined to be ill-conditional, additional cost and labor on unnecessary wafer amendment can be inevitable. In the case that an unqualified wafer passes the examination, further loss in the sequent manufacturing processes can be foreseen. Obviously, in examining the periphery ring of the wafer after a coating process, neither above case is welcome.